PS-2 Power Amp output impedance mismatch

Stage & Studio Power Station PS-2
1

Hello Fryette,

I hope you’re having a fantastic day.

I’m using the PS-2A in combination with an amp switcher.
Most of the tube amps have 8 ohms output impedance but one has 4 ohms.
Most of cabs are 8 ohms, except one which is 4 ohm.

As the PS-2A is racked, I can’t easily access the Amp and Speaker impedance selector switches on the back (#9 and #11 in user manual rear diagram).
If I set both of them to 8 ohm, I’ll cover proper match for most of the configurations. Only the 4 ohm amp and cab will mismatch.

I’m happy to send the 4 ohm amp to the PS-2A 8 ohm load.

But I’m concerned about mismatching the PS-2A power amp itself with a lower impedance.
Can the PS-2A power amp safely accept being loaded with 4 ohms while having the speaker impedance selector set to 8 ohm?

Thank you!

2

Hi Ludovic. Welcome to the forum!

Most people don’t really understand how and when an impedance mismatch becomes a serious problem, which drives the concern about breaking something.

The short answer is, no, you will not damage the PS-2 simply because of a mismatch. Damage occurs when mismatched gear is pushed to extreme operating conditions. Most of the time the PS-2 and PS-100 are not even working hard, so the likelihood of damage is practically zero.

What you may experience is a slight shift in the low and midrange frequency response and a very small reduction in maximum output power.

Cheers,

Dave

1 Like
3

Hi Dave,

Thanks a lot for your help.

I was assuming this as Mesa Boogie even recommend to test the effect of such mismatch for tone.

I read that impedance mismatch has a direct effect on voltage (V=RI) on the circuit before the primary of the OT (mismatch up, less voltage on primary, mismatch down, more). But I don’t know how much and what are the tolerances of the PS-2A power amp. In doubt, I preferred asking.

Now I am completely reassured.

Thank you!!